BRD-PREY

iTrader: (5)

If this is correct it would be a significant improvement in ground clearance!

My thought is a 2" or even 1.5 inch exhaust cutout would be as effective as a full size 3" cutout. I figure that since its not an exhaust divertor that it only needs to aloow enough additional flow as to remove excess backpressure.
The original 3"-4" and muffler are still flowing so the cutout just needs to provide that extra flow above what they are capable.
This would make it much easier to fit under the car.

Please chime in if you see a flaw or agree with this conclusion.

Thanks
ed

I talked to a design engineer with Borla and he seems to think it would be fine with a smaller cutout.
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Element

iTrader: (5)

I don't think it would be "as effective" but I don't think you'd see much loss going with a 2" over a 3" cutout, at least with a smaller-cube engine. A 1.5" would really be pushing it.

jimmyblue

iTrader: (11)

You don't present a conclusion with any clarity, only
that it would be "good enough". Which might be true
for you, given low enough expectations. But you seem
to be asking us to validate your value judgment, not
any particular facts. Because the fact is that a 3" orifice
has less backpressure@flow than a 2". You want to say
the difference doesn't matter, go right ahead. Just be
sure to mention "to you".

BRD-PREY

iTrader: (5)

I did not mean to offend you, as your were one of the considerate few to comment on the original thread.

That being said, Just where did I ever say a "3" orifice
has less backpressure@flow than a 2". That contradicts itself less backpressure and less flow!!

I was hoping an engineer or someone with flow calculation experience would chime in and either agree or disagree and point out the flaws in my logic.
I was hoping to share my idea and get some feedback.

BUT to clarify: The exhaust is 3" pipe, 2 of them flow into a 4" flowmaster merge and then travel through 3" pipe to a muffler. I have 2) 3" cutouts mounted in the y-pipe. When they are open the exhaust now has a 6" opening each. Each side of the Y-pipe has a cutout. The flow can go down the traditional path to the merge and muffler or out through the cutout to to a down turn.

Since this means (yes. I realize slightly less) each header has 6" of flow path.
this seems like way overkill! I would think a smaller cutout and my original low restriction exhaust system combined would still be more than enough for my LS3 417

BRD-PREY

iTrader: (5)

You realize you would have both the 2" cutout and the 3" exhaust piping would be flowing the exhaust. This is in theory has more flow capacity the the 3" header collector that came on my 17/8 Kooks. So, it should equal OPEN headers.

Now I also acknowledge that open headers are not the best choice but remember the choice is between 3" or 2" cutouts.

Element

iTrader: (5)

You're not calculating flow disruption, among other variables. It also won't equal open headers, because you're still flowing into a curved pipe, which creates vortex issues, wall turbulence, etc.

From a flow standpoint, no, a 2" cutout isn't going to have nearly the flow potential as a 3" cutout. From a real-world standpoint, the 2" cutout will probably pick up a little power at the top, and if you're really limited as far as ground clearance and it's a 2" or nothing, then it's better than not running one; however, it would be ignoring physics to say that a 2" cutout is going to flow as well as a 3", regardless of any other conditions.

That said, if you're not going max effort, and ground clearance is an issue, a 2" cutout would probably be sufficient for your situation.